CONDENSED CONSOLIDATED STATEMENTS OF INCOME (LOSS) AND COMPREHENSIVE INCOME (LOSS) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
CONDENSED CONSOLIDATED STATEMENTS OF INCOME (LOSS) AND COMPREHENSIVE INCOME (LOSS)
Operating revenue	$ 158,505	$ 126,773
Operating expenses:
Salaries, wages and employee benefits	36,555	35,845
Fuel and fuel taxes	11,444	11,863
Depreciation and amortization	9,570	10,011
Insurance and claims	5,809	5,857
Equipment rent	1,949	2,292
Operations and maintenance	7,066	8,896
Purchased transportation	74,103	47,814
Operating taxes and licenses	1,272	1,159
Communications and utilities	804	813
(Gain) loss on disposal of assets, net	(177)	38
Other	4,064	4,497
Total operating expenses	152,459	129,085
Operating income (loss)	6,046	(2,312)
Other expenses:
Interest expense, net	1,025	1,684
Other, net	61	46
Total other expenses, net	1,086	1,730
Income (loss) before income taxes	4,960	(4,042)
Income tax expense (benefit)	1,363	(1,491)
Consolidated net income (loss) and comprehensive income (loss)	$ 3,597	$ (2,551)
Net earnings (loss) per share:
Average shares outstanding (basic) (in shares)	8,841	8,633
Basic earnings (loss) per share (in dollars per share)	$ 0.41	$ (0.30)
Average shares outstanding (diluted) (in shares)	9,007	8,633
Diluted earnings (loss) per share (in dollars per share)	$ 0.40	$ (0.30)